In a next generation mobile communications network, user equipment accesses the network by using a local radio access network. A mobility management network element is responsible for functions such as location management, connection management, security authentication, and gateway selection of the mobile user equipment. A serving gateway is a local access gateway of the user equipment and is responsible for connection management and data forwarding that are related to an access technology. A data gateway is a gateway through which the user equipment accesses an external data network.
Because after a network device (a serving gateway and/or a data gateway) is reset, user information on the reset serving gateway and information about a PDN connection on the reset data gateway are lost. Therefore, after a downlink data packet of a user arrives at the reset network device, the reset network device discards the data packet because a specific user and information about a PDN connection cannot be found. When the downlink data packet corresponds to a relatively important service such as a called voice call, reset of the network device may cause a failure of the called voice call, and therefore, satisfaction of the user on a network is reduced, and user experience is affected.